The chemical industry utilizes numerous processing techniques in which intimate contact of physically disparate phases is of necessity promoted to optimize the chemical reactions sought to be achieved. Typically, these reactions take place in the liquid phase, and consequently a wide variety of devices have been developed for dispersing gases in liquids.
In typical gas-liquid reactors, a gas is introduced into the bottom of a reactor through an open-ended standpipe, orifices in a horizontally perforated pipe or perforated plate, or through orifices in a perforated sparger ring. The orifices in these devices generally range in size from about 1/4 inch to 1 inch. At ordinary gas flow rates, therefore, the size of the gas bubbles generated is also in the range of about 1/4 inch to about 1 inch in diameter and, hence, are relatively quite large.
In order to generate smaller bubbles, it is commonly believed that it is necessary to reduce the orifice size. Indeed, foraminous materials, i.e. porous plates and the like that have a plurality of
pores all having pore sizes generally less than 1 mm in diameter or length, have been proposed as suitable fine bubble generators. Use of foraminous surfaces as gas bubble generators suffer from several significant disadvantages. Among these is the significant pressure drop associated with use of such devices. Another disadvantage is the ease with which the foraminous material can be fouled or plugged.
Aspirators also have been used for dispersing a gas in a liquid. In these types of devices a liquid is pumped at a rapid rate through a nozzle and the gas is aspirated through a venturi, for example, and thereby dispersed in a liquid stream. In such systems, however, the gas to liquid ratio generally is low, for example, up to about 1:1. Other disadvantages of aspirators are well known.